Method for fabricating adhesion-resistant micromachined devices

ABSTRACT

A method for fabricating an adhesion-resistant microelectromechanical device is disclosed wherein amorphous hydrogenated carbon is used as a coating or structural material to prevent adhesive failures during the formation and operation of a microelectromechanical device.

TECHNICAL FIELD

This invention is related to the use of amorphous hydrogenated carbon asa micromachined structure or as a coating on micromachined structureswhich prevents adhesion failures.

BACKGROUND ART

Micromachined structures have become increasingly important for avariety of applications. Movable mechanical elements such ascantilevers, beams, and diaphragms are often micromachined for sensorsand actuators. Surface micromachining is a microfabrication technologythat has attracted great attention, partly because it can producemicromachined structures that can be integrated with electronic devices.With this technology, a sacrificial layer, such as silicon oxide, isfirst deposited and patterned on a substrate, usually a silicon waferalready coated with silicon nitride. The film for the microstructure isthen deposited and patterned. The sacrificial layer is then etched awayto release the microstructure, leaving it freely suspended and anchoredonly where it directly contacts the substrate through the patternedopening of the sacrificial layer.

The large surface area to volume ratios of these microstructures,whether processed by surface micromachining, bulk micromachining, waferdissolving and bonding process, or LIGA process, however, result inproblems associated with unwanted adhesion between adjacent elements.Such adhesive failures have a direct impact on production yield andreliability of these devices.

The sticking of freely standing microstructures to the substrate is aprincipal source of failures in surface micromachined devices. Stictionoccurs both immediately after the sacrificial etch release process andduring operation of the device. During the rinse process and afterrelease of the sacrificial layer by the wet etch process, the capillaryforce from the rinse liquid causes attraction between suspended elementsof the device and the underlying substrate which causes these elementsto adhere to the underlying substrate. Even after a successful release,problems with stiction may still arise if the microstructure is exposedto liquid, from any subsequent wet process, or water vapor condensationduring device operation.

Previous approaches may reduce the likelihood of an adhesion failure tosome degree but fail to eliminate the problem altogether. An example ofa proposed approach is described in the Abe et al. reference, publishedin the Proc. IEEE Mems Workshop, p. 94, published on Jan. 29, 1995 inthe Netherlands. This reference describes a process whereby the surfacecontact area is reduced by introducing bumps at the bottom of thesurface of the freely standing structure. Another approach is publishedin Transducers '93, p. 288, by Alley et al., 1993 in Yokohama, Japan.The Alley et al. reference outlines different ways of increasing surfaceroughness of the substrate to reduce the real surface contact area. Inanother publication by Mulhern et al., Transducers '93, p. 296, 1993 inYokohama, Japan, there is discussed a method of using super criticalcarbon dioxide drying to prevent stiction by eliminating capillaryforces from the rinse liquid. However, this approach cannot eliminatepost-rinse stiction problems. Yet another approach is presented byHouston et al. in Proc. of the 8th International Conference onSolid-State Sensors and Actuators, p. 210, Stockholm, Sweden, June 1995,wherein ammonium fluoride is used to treat a polysilicon structuresurface to obtain a passivated hydrogen terminated surface. However, inthe presence of air, the polysilicon surface oxidizes in less than oneweek and loses all the benefits from the treatment.

There thus remains a need for a method of reducing and preventing thestiction of micromachined structures for the life of a micromachineddevice.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide atechnique for preventing and reducing adhesion failure both during thefabrication and operation of micromachined structures.

In addressing this need, the present invention discloses a process thateither incorporates a coating for micromechanical structures includingamorphous hydrogenated carbon (AHC) or doped amorphous hydrogenatedcarbon, or uses amorphous hydrogenated carbon to form micromechanicalstructures. Both approaches serve to reduce adhesive forces and thusprevent adhesion failure, as well as provide low friction and wearbetween the microelectromechanical structure and the underlyingsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of a vacuum apparatus andassociated equipment for applying a coating of AHC or depositing astructural layer of AHC by a plasma enhanced chemical vapor deposition(PE-CVD) method that employs radio frequency techniques.

FIG. 2 illustrates a cross sectional view of one embodiment of amicromechanical device that is conformally coated with an amorphoushydrogenated carbon coating.

FIG. 3 illustrates a cross sectional view of another embodiment of amicromechanical device in which the microstructure is made of amorphoushydrogenated carbon.

FIGS. 4-10 illustrate cross sectional views of step by step constructionof the devices illustrated in FIGS. 2 and 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention teaches the use of amorphous hydrogenated carbon(AHC) as a protective coating on microelectromechanical structures(MEMS) or as a microelectromechanical structure to prevent the stickingof such microstructures to a substrate during fabrication or subsequentprocesses.

The term microelectromechanical structure as used herein is intended toinclude movable mechanical microstructure elements used in actuators,sensors, and other micromechanical devices.

While not wishing to be bound to any particular theory, it is believedthat the use of amorphous hydrogenated carbon as a coating or as thestructural layer serves to reduce adhesive forces in part due to thechemical inertness of the carbon composition. It is believed that thedominant forces acting between surfaces are capillary forces caused bymeniscus formation. Capillary forces are created in polysiliconstructures because silicon or polysilicon forms an oxide in air, whichcauses a hydrophilic surface. This hydrophilic surface attracts waterwhich, in turn, causes an attraction between the microstructure and thesubstrate and results in stiction after drying.

This invention serves to reduce the adhesive forces betweenmicrostructure surfaces by altering their surface properties. Thesurface treatment or application of AHC is thus designed to create ahydrophobic surface. The hydrophobic nature of AHC means that watertends to repel itself from an amorphous hydrogenated carbon surface.Accordingly, in a MEMS device, the use of AHC as a protective coating oras a MEMS structure results in lower capillary forces and an associatedreduction in stiction.

From an experimental viewpoint, a coating of AHC produces a surface witha low wetting or sticking tendency as measured by the "contact angle"between the coated surface and a droplet of water in a standard testapparatus. With the contact angle test, the attractive forces, or theadhesive energy between the liquid drop resting on a particular surfaceis revealed by the contact angle that the liquid makes with thatsurface. With a greater contact angle, there is a decrease in theadhesive force, as is discussed in "Network Modifications of DLCCoatings to Adjust a Defined Surface Energy" by K. Trojan et al. inPhysics Status Solid, Vol. 145(a), p. 575, 1994. Our research indicatedthe contact angle of water on Si-containing AHC is about 85°, muchlarger than the 35° contact angle of water on silicon with a nativeoxide layer. The chemical inertness of AHC also helps to reduce anyadhesion caused by inter-solid chemical interaction that bonds themicrostructure to the substrate.

In addition to the anti-adhesion properties of AHC, there are othersignificant benefits associated with the use of AHC in conjunction withMEMS. As an example, the use of AHC as a protective coating onmicroelectromechanical structures serves to significantly reduce thefriction generated by moving parts. Friction is another major designconcern in microelectromechanical systems with moving parts, such asmicromotors, microvibrators, or microresonators. Due to the reducedsizes and forces, the effect of friction forces in MEMS is even moresignificant than in macro devices. AHC's low coefficient of friction, inthe range of 0.05-0.1, is thus a valuable property.

The use of AHC also results in a marked reduction in the wear of MEMSmoving parts. Like friction, wear is another factor that directlyaffects the performance of these systems. The wear rate of AHC istypically in the range of 10⁻⁸ to 10⁻⁶ mm³ /Nm.

Notwithstanding the beneficial friction and wear properties, AHCprovides high hardness, in the range between 12-20 GPa, and high Young'smodulus, in the range between 120 to 180 GPa. Such mechanical propertiesmake AHC a good material for mechanical structures in many MEMSapplications. Cantilevers, beams, and membranes, and many othermicromechanical elements can be made of AHC to take advantage of bothsurface and bulk properties of AHC.

The use of AHC for MEMS is further understood to prevent corrosioncaused by humidity and other chemicals, due to the chemical inertness ofthe carbon composition. AHC is not etched significantly in almost allacids and bases, such as hydrofluoric acid, hydrochloric acid, sulfuricacid, nitric acid, sodium hydroxide and potassium hydroxide.Furthermore, amorphous hydrogenated carbon is a good insulator.Accordingly, AHC may also be used as a diffusion barrier insemiconductor devices.

In addition, experimental evidence has demonstrated that AHC adhereswell to silicon, polysilicon, silicon dioxide, silicon nitride and manymetal substrates, such as aluminum, titanium, and tungsten without useof an interlayer. This allows AHC to be used in a variety ofapplications for MEMS systems.

With this invention, amorphous hydrogenated carbon can be used to createthe microelectromechanical structure or as a protective coating formicroelectromechanical structures to provide a hard, low-wear andlow-friction, chemical-inert material, which most importantly solves thestiction problem plaguing current micromachining processes.

The coating of the present invention, which creates an adhesionresistant surface, can be selected from the following group: amorphoushydrogenated carbon and doped hydrogenated carbon. The list of possibledopants, that are found to increase contact angle, include, but are notlimited to, silicon, fluorine, boron, nitrogen, oxygen, niobium,tungsten, titanium, and tantalum.

The preferred coating or structural composition formicroelectromechanical structures is silicon-doped amorphoushydrogenated carbon. Si-AHC is the preferred coating because of itsthermal stability and ability to withstand humidity. Incorporation ofsilicon in AHC also reduces compressive stress in the film andfacilitates deposition of AHC films up to at least 12 microns thick.

The amorphous hydrogenated carbon is formed from a hydrocarbon source,such as, for example: ethane, ethylene, acetylene, methane, butane,propane, hexane, benzene, toluene, xylene, and combinations thereof. Anamorphous hydrogenated carbon coating of the present inventionpreferably has up to 20-60 atomic percent of hydrogen and mostpreferably between 35 and 50 atomic percent of hydrogen to achieve a lowcoefficient of friction. The AHC coating preferably is 100 Angstroms to10 microns in thickness. Most preferably, the AHC coating has athickness of between 500 Angstroms and 5000 Angstroms.

From a manufacturing standpoint, the amorphous hydrogenated carboncoating can be detected using laser Raman spectroscopy. Since AHCcoatings yield a broad band at around 1500 cm⁻¹ and a shoulder band ataround 1400 cm⁻¹ qualitative analysis using laser Raman spectroscopy ispossible.

As a protective coating, amorphous hydrogenated carbon film can beconformally coated on microstructures in sensors and actuators aftertheir fabrication. The amorphous hydrogenated carbon film coatings ofthe present invention can be applied by various techniques, includingdirect current, radio frequency, plasma-assisted chemical vapordeposition, ion beam deposition and arc discharge techniques.

While a number of different methods may be used to deposit thesecoatings onto a substrate, a preferred deposition method, involves a lowpressure, plasma enhanced, chemical vapor deposition (PE-CVD) technique.The amorphous hydrogenated carbon is preferably deposited using theplasma deposition process disclosed in U.S. Pat. Nos. 5,237,967,5,249,554 and 5,309,874 assigned to the Ford Motor Company. Thedisclosures of these three Ford patents are incorporated herein forreference.

As provided in FIG. 1, this low pressure, on the order of 1-100milliTorr, deposition is carried out in a vacuum chamber 10 where an RFpower supply 12 is capacitively coupled with a coupling capacitor 14 toelectrodes whose electrical activation sustains the plasma 16 amongappropriate precursor gases 18 admitted to the vacuum chamber 10 througha gaseous flow rate controller 20. One electrode is the substrate 22 tobe coated, shown schematically as a silicon wafer, in combination with asupport structure 24, while the other electrode in the simplest case, isthe grounded wall of the vacuum system which surrounds, but iselectrically insulated from the substrate 22.

The precursor gases 18 include at least one hydrocarbon species such asmethane or other hydrocarbon gases to form the amorphous hydrogenatedcarbon. Other gaseous constituents can be included in appropriateproportions, for example, gases of silicon compounds can be included toprovide a silicon dopant for the AHC film coating. Examples of the gasesof silicon compounds include those of silicon tetrachloride, SiCl₄,silicon tetrafluoride, SiF₄, trichlorosilicon, SiHCl₃, andtetramethylsilicon, Si--(CH3)4.

In operation, the different electrical mobilities of the electrons andions formed within the plasma results in the development of a negativepotential on the substrate relative to the plasma, a "self bias" whichacts to beneficially accelerate positive species composed of ionizedprecursors or gas constituents to the substrate where they react to formthe desired coating. Important coating properties such as hardness,coefficient of friction, internal stress and the like are a function ofthe self bias potential. The self bias, which is not strictly a DCpotential but has an alternating component at the applied RF frequency,is itself a function of many process parameters including pressure, gascomposition, electrode shape, and the like, and is measuredapproximately during operation by measuring the potential between thesubstrates and ground. Optimum coating properties such as hardness, wearand coefficient of friction were found for self bias potential in therange from 200 V rms to 800 V rms, which corresponds to an averagekinetic energy for carbon ions impacting the substrate of between 50 to200 electron volts.

The PE-CVD technique is particularly advantageous for a number ofreasons. First, it is a conformal technique in that the plasma surroundsor conforms to the surface of the structures which act as one of theelectrodes for exciting the plasma. As a result, a complex surface of aMEMS structure may be coated with a uniform coating. This can not beachieved if a unidirectional ion beam coating technique is utilized evenwith rotation of the wafer.

In addition, the PE-CVD approach can be accomplished, by expending asmall amount of power per unit surface area of substrate, at a substratetemperature that may be constrained in the range of 100° C. to 200° C.This temperature range does not cause any major concerns for materialsand device structures already fabricated before the coating step.

As depicted in FIGS. 2 and 3, in surface micromachining, themicromachined device 34 typically consists of a silicon substrate 26that may be coated with a passivating layer of silicon dioxide 28 andsilicon nitride 30. A patterned layer 32 is applied on the substrate 26or the coated substrate 30, as depicted. The device further includes astructural layer 40 in mating contact with the patterned layer. Desiredmicrostructures are formed from the structural layer.

As depicted in FIG. 2, AHC can be conformally coated on themicromachined device 34 such that the at least one microstructure formedfrom the structural layer and the substrate are coated with theamorphous hydrogenated carbon coating 42. As depicted in FIG. 3, thestructural layer 40 can alternately be made of amorphous hydrogenatedcarbon. With either embodiment, an adhesion, friction and wear-resistantmicromachined device is fabricated.

In the following section, two examples illustrate the incorporation ofAHC as a passivative coating for micromachined structures. The firstexample demonstrates post-process application of AHC as a protectivecoating to passivate a fabricated microelectromechanical device. Thesecond example illustrates use of AHC to fabricate a micromachinedstructure. Though simple cantilever structures are used in both examplesfor demonstration purpose, it is clear that this invention can beapplied in the same spirit to any microelectromechanical devices,including sensors such as accelerometers and pressure sensors, oractuators such as linear vibrators, rotational motors, as well as othermicromechanical devices that having moving parts.

Example 1 Application of AHC as a Protective Coating on MicromachinedStructures

In this example, AHC is used to coat a surface micromachined device 34,as depicted in FIG. 2, consisting of a substrate 26, a patternedpolysilicon layer or bottom electrode 32, and a movable micromachinedcantilever structure 40.

As illustrated in FIG. 4, a silicon wafer 26 is coated with an optionalthermal silicon dioxide layer 28, which serves as a passivating layer,preferably having a thickness of 5000 Angstroms. While the substrate inthis example is silicon, numerous other substrates function effectively.Possible substrates include, but are not limited to, quartz, glass,aluminum oxide and other such materials. A silicon nitride coating 30 isthen applied to serve as a passivating layer onto the silicon substrate26 or the silicon substrate 26 with a silicon dioxide layer 28. Thesilicon nitride layer 30 preferably has a thickness in the range of 500Angstroms to 1500 Angstroms.

In the preferred embodiment, the substrate is coated with a passivatinglayer. This passivating layer serves as an insulating medium between thesubstrate and the patterned layer, which provides electricalinterconnections for the microstructure. Depending on the substrateselected, the following passivating layers are preferred: siliconnitride and silicon dioxide. In the most preferred embodiment, where asilicon substrate is utilized, two passivating layers are preferred sothat the substrate is first coated with a silicon dioxide layer followedby a silicon nitride layer. Again, the selection of the passivatinglayer is linked to the selection of the substrate, and thus, dependingon the substrate selected, one or more passivating layers may bepreferred.

As depicted in FIG. 5, a patterned layer of phosphorous-dopedpolysilicon 32 is deposited by low- temperature chemical vapordeposition (LPCVD) at 600° C., the phosphorous-doped polysilicon layer32 having a preferred thickness of 3000 Angstroms. This polysiliconlayer 32 is next preferably patterned with a first mask by reactive-ionetch in a chlorine plasma. This patterned polysilicon layer 32 serves asa bottom electrode and provides electrical interconnections for the MEMSdevice. For example, where the MEMS device is a capacitor or the like,the patterned layer may serve as a bottom electrode. As the electricalconnecting layer, the patterned layer should be made of a conductivematerial. Accordingly, the most preferred composition for the patternedlayer is polysilicon. Other preferred materials for the patterned layerinclude such metals as tungsten, aluminum, chromium, palladium, andgold.

As further depicted in FIG. 6, an LPCVD sacrificial layer 36, preferablymade of a phosphosilicate glass (PSG), has a preferred thickness betweenone micrometer and six micrometers, is deposited at 450° C. anddensified at 950° C. for one hour, followed by a second masking stepthat exposes an anchor 38. The anchor 38 provides contact between thestructural layer 40 and the patterned layer 32.

As illustrated in FIG. 7, a structural layer 40, preferably a thickdoped polysilicon layer, is next deposited, preferably having athickness between 1 micrometer and 5 micrometers using an LPCVD methodat 610° C. This polysilicon structural layer 40 is next annealed at1000° C. to release structural stress. The polysilicon layer 40 is nextpatterned by a third mask to form a top electrode and the desiredmicrostructures. The sacrificial layer 36 and the structural layer 40work together, since the sacrificial layer 36 is removed to release themicrostructures within the structural layer and thus the composition ofthe two layers is inextricably linked. The relationship of thesacrificial layer to the structural layer should be such that when thesacrificial layer is etched off, the overlaying structural layer 40remains intact.

Accordingly, where the structural layer 40 is polysilicon, the preferredsacrificial layer is phosphosilicate glass. Other pairing combinationsinclude, but are not limited to, a silicon nitride structural layer witha polysilicon sacrificial layer and a nickel structural layer with analuminum sacrificial layer.

Where a multi-layer microstructure is desired, such as, for example, aparallel capacitor, the sacrificial layer 36 and the structural layer 40can be repeated. Accordingly, for such multi-layer microstructures, thestructural layer 40 will have a second sacrificial layer and a secondstructural layer applied thereon to create the desired multi-layermicrostructure.

The wafer is then immersed in a wet etching solution, such as inhydrofluoric acid or buffered HF acid solution to remove the sacrificialPSG layer 36, as depicted in FIG. 8. Following this step, the wafer isproperly rinsed and preferably dried using a supercritical carbondioxide sublimation process. Depending on the sacrificial layerselected, the etching solvent will of course vary.

An AHC layer 42 is next applied conformally to cover the microstructures40, and the substrate as depicted in FIG. 2, in a plasma-assisted CVDprocess. The AHC layer 42 is preferably applied to have a thicknessbetween 500 Angstroms and 5000 Angstroms, with a most preferredthickness of 1000 Angstroms. The AHC layer 42 is preferably depositedusing methane as a precursor gas, with a flow of 30 sccm at a pressureof 20 millitorr. The sample is self-biased through the RF power supplyat 500 Volts. FIG. 2 shows a finished micromachined device with an AHCcoating.

The presence of the AHC coating on the substrate effectively prevents orreduces sticking failures during operation of the fabricated MEMSdevices.

Example 2 Application of AHC as a Micromachined Structure

In this example, application of AHC is incorporated in a surfacemicromachining process to form a movable cantilever that is made of AHC.

The first three steps of this process consist of preparing a substrate26, such as a silicon wafer with a silicon dioxide coating 28 and asilicon nitride coating 30, to provide two passivated coatings,depositing a patterned polysilicon layer 32, and depositing andpatterning a sacrificial layer 36 made of PSG, which is described indetail in the section above and as shown in FIGS. 4-6.

As further depicted in FIG. 9, a release layer 44, such as a photoresistlayer, is then spun on to the micromachined device 34, preferably havinga thickness between one micrometer and six micrometers, followed by aphotolithography step that defines the overlaying AHC coating. Therelease layer, most preferably a photolithography patterned photoresistlayer, facilitates patterning of the AHC layer. With this preferredembodiment, solvent will attack the photoresist layer and remove the AHCdeposited on top of the photoresist layer, while leaving the AHCdeposited underlying material to form patterned structures.

A structural layer of a thick film of amorphous hydrogenated carbon 40and 42 is next deposited, as shown in FIG. 10, preferably having athickness between 1 micrometer and 5 micrometers. The AHC structurallayer 40 and 42 is preferably deposited using methane as a precursorgas, with a flow of 30 sccm at a pressure of 20 millitorr. The sample isself-biased through the RF power supply at 500 Volts.

The substrate 26 is first immersed in a solvent, such as acetone, toremove the release layer. The AHC layer 42 overlaying the release layer44 is removed by a "lift-off process", leaving only a patterned AHCstructural layer 40. The substrate 26 is then immersed in an etchingagent such as hydrofluoric acid or buffered HF acid solution to removethe sacrificial PSG layer 36. Depending on the sacrificial layerselected, the etching solvent will of course vary. Following this step,the wafer is properly rinsed in deionized water and dried, as depictedin FIG. 3.

Where the microstructure consists of AHC, there is required a method forpatterning the AHC depending on the desired microstructure. Aspreviously mentioned, AHC is preferably patterned by a lift-off process,whereby an AHC film is deposited on a photolithography patternedphotoresist release layer. Subsequent investigations also indicate thatit is possible to pattern AHC by plasma etch in chlorine or fluorinebased chemistry using a patterned photoresist layer as a maskingmaterial, which can be stripped later in a solvent or oxygen plasma.

While the most preferred release layer consists of a photoresist layer,polymers such as polyamides, pyridine, and the like are also suitable,as long as the polymer selected is composed of a material which can beetched by a solvent without the underlying AHC structural layer beingsimultaneously etched. Similarly, the etching solvent must not attackthe underlying AHC structural layer. The following is a list of somesuitable acids and bases: hydrofluoric acid, hydrochloric acid, sulfuricacid, nitric acid, sodium hydroxide, and potassium hydroxide.

The presence of the AHC layer on the substrate effectively prevents orreduces sticking failures during the rinse and drying process thatfollow the release of the polysilicon structure. The AHC microstructurewill also prevent or reduce sticking failures during operation of theMEMS device.

Although the examples only illustrate the incorporation of amorphoushydrogenated carbon coating with surface micromachined structures, thosewho are familiar in the art to which this invention relates willrecognize that the spirit of this invention can be equally applied toother micromachined processes, including but not limited to bulkmicromachining, wafer bonding and wafer dissolving, and LIGA-likeprocess.

While the best mode and viable alternate embodiments for carrying outthe invention have been described in detail as shown on the drawings,those skilled in the art to which this invention relates will recognizevarious alternative designs and embodiments for practicing the inventionas defined by the following claim.

What is claimed is:
 1. A method of forming an adhesion-resistantmicromachined device, comprising the steps of:providing a substrate:applying a patterned layer on said substrate; applying a sacrificiallayer on said patterned layer; applying a structural layer on saidsacrificial layer to create at least one micromachined structure;removing said sacrificial layer to release said at least onemicromachined structure from said structural layer; and applying anamorphous hydrogenated carbon coating on said micromachined device, suchthat said at least one micromachined structure and said substrate arecoated with said amorphous hydrogenated carbon consisting to preventadhesion failure.
 2. The method of claim 1, wherein said substrate isselected from the group consisting of silicon, glass, quartz, andaluminum oxide.
 3. The method of claim 1, wherein said substrate iscoated with a substrate coating selected from the group consisting ofsilicon nitride, silicon dioxide and the combination of silicon nitrideand silicon dioxide.
 4. The method of claim 1, wherein said methodfurther includes the step of applying on said structural layer a secondsacrificial layer and a second structural layer to create a multi-layermicrostructure.
 5. The method of claim 1, wherein said structural layeris selected from the group consisting of polysilicon, silicon nitrideand nickel.
 6. The method of claim 1, wherein said amorphoushydrogenated carbon coating is a doped amorphous hydrogenated carbonselected from the group consisting of silicon-doped amorphoushydrogenated carbon, fluorine-doped amorphous hydrogenated carbon,boron-doped amorphous hydrogenated carbon, nitrogen-doped amorphoushydrogenated carbon, oxygen-doped amorphous hydrogenated carbon,niobium-doped amorphous hydrogenated carbon, tungsten-doped amorphoushydrogenated carbon, titanium-doped amorphous hydrogenated carbon andtantalum-doped amorphous hydrogenated carbon.
 7. The method of claim 1,wherein said sacrificial layer is removed with an etching solventselected from the group consisting of hydrofluoric acid, hydrochloricacid, sulfuric acid, nitric acid, sodium hydroxide, potassium hydroxideand an aluminum etchant.
 8. The method of claim 1, wherein saidsacrificial layer is selected from the group consisting ofphosphosilicate glass, silicon, polysilicon and aluminum.
 9. The methodof claim 1, wherein said amorphous hydrogenated carbon coating is 1000Angstroms in thickness.
 10. The method of claim 1, wherein saidamorphous hydrogenated carbon coating is 500 to 5000 Angstroms inthickness.
 11. The method of claim 1, wherein said amorphoushydrogenated carbon coating is applied by a chemical vapor depositiontechnique.
 12. The method of claim 1, wherein said amorphoushydrogenated carbon coating is formed form a hydrocarbon source selectedfrom the group consisting of ethane, ethylene, acetylene, methane,butane, propane, hexane, benzene, toluene, xylene and combinationsthereof.
 13. The method of claim 1, wherein said amorphous hydrogenatedcarbon coating comprises hydrogen having a concentration of 20-60 atomicpercent.
 14. The method of claim 1, wherein said amorphous hydrogenatedcarbon coating comprises hydrogen having a concentration of 35-50 atomicpercent.
 15. The method of claim 1, wherein said amorphous hydrogenatedcarbon coating yields a broad band at around 1550 cm⁻¹ and a shoulderband at around 1400 cm⁻¹ when detected by laser Raman spectroscopy. 16.The method of claim 1, wherein said step of applying an amorphoushydrogenated carbon coating further comprises:placing said substrate ina vacuum chamber; evacuating gas within said vacuum chamber;establishing a reactive gas mixture within said vacuum chamber, whereinsaid reactive gas mixture is selected from the group consisting ofgaseous silicon compounds, gaseous hydrocarbon compounds and mixturesthereof; and establishing a plasma discharge within said vacuum chamber,such that said substrate is an electrode in said plasma discharge andsaid amorphous hydrogenated carbon coating is deposited on saidsubstrate.
 17. The method of claim 16, wherein said step of applying anamorphous hydrogenated carbon coating is maintained at a temperatureless than 200° C. to avoid thermal alterations of said substrate. 18.The method of claim 16, wherein said gaseous silicon compounds areselected from the group consisting of: diethylsilane, silicontetrachloride, silicon tetrafluoride, trichlorosilicon, andtetramethylsilicon.
 19. The method of claim 1, wherein said patternedlayer is selected from the group consisting of polysilicon, tungstsen,aluminum, chromium, palladium and gold.
 20. A method of forming anadhesion-resistant micromachined device, comprising the stepsof:providing a substrate; applying a patterned layer on said substrate;applying a sacrificial layer on said substrate; applying a release layeron said sacrificial layer; forming an amorphous hydrogenated carbonstructural layer on said release layer; removing said release layer topattern said amorphous hydrogenated carbon structural layer; andremoving said sacrificial layer to release at least one micromachinedstructure from said amorphous hydrogenated structural layer.
 21. Themethod of claim 20, wherein said release layer is a photolithographypatterned photoresist layer.
 22. The method of claim 20, wherein saidrelease layer is a polymer selected from the group consisting ofpolyamide and pyridine.
 23. The method of claim 20, further comprisingthe step of patterning said sacrificial layer with a wet etch solvent toprovide contact for anchoring said at least one structural layer. 24.The method of claim 20, further comprising the step of patterning saidamorphous hydrogenated carbon structural layer with a mask to form saidat least one micromachined structure.